The Gentleman's Quest: inspirational historical romance (Journeys of the Heart Book 1) by Camille Elliot

Honoria hasn't had a good relationship with men since her brother's death.  First her cousin took over the house they lived in and thrust them out because she wouldn't accept his advances.  Then her mother's brother let them live with them but complained every day.  To get her mother and herself out of that household, she will have to marry.  She has no dowry.  She's not beautiful.  The man who wants to marry her is old and lecherous.  But he wouldn't be as bad as the other two.

Wild Heart Books let me read this book for review (thank you).  It has been published and you can grab a copy now.

Then a male friend from her past comes to visit.  He's been avoiding her but he found one of her brother's belongings with a dead man in his barn.  He's returning it.  When he shows them there is a map inside, Honoria hopes it's for a treasure.  If it is, maybe she won't have to marry!

As they pursue clues to identify the map location, they have folks following them and trying to steal the map.  It turns into a dangerous venture both with the map and with their hearts...